hi Sajid,
            Just some thoughts.....
    The solution seems to be a high throw mixture (I think that's good for
your geometries) but your Cl- of 0.166mg/L seems very low, usually its in
the 50-80ppm range (=50-80mg/L). Some companies sell different additive and
solution specs. for DC, pulse or pulse reverse, make sure you have spoken to
them about your application (the Cl- concentration might be correct for this
additive system and/or maybe the additive system might not be ideal for
pulse reverse plating). Your pulse setting sound off too, they are too
similar. Usually its a long FORW. ~20ms and a short higher current density
REV ~1ms  (there's a lot more to this but this seems to be the basics and in
no way is 20ms and 1ms magic numbers).
            Some useful thoughts...... :)
1)Google search "pulse reverse copper plating"
2)Have you heard of the DOE software called JUMP? Do a small DOE varying
FORW., OFF, REV times and FORW, REV. current density and let the data lead
you to optimization.
Hope this helps. good luck,
                                                 eric


> Message: 7
> Date: Sun, 7 Sep 2003 21:00:46 -0500
> From: "sajid" 
> Subject: [mems-talk] Cu electroplating; sorry if you received this
> mail twice

> Hi,
>
> I need some help with Copper electroplating.
>
> I have 30 micron wide and 60 micron deep trenches in silicon and I need
> to electroplate copper into the whole trench. However, after a certain
> duration of plating, my trench gets closed off and I get voids in them.
> The best I've been able to get is a ratio of 2 in the thickness
> uniformity. That is 12 microns on each sidewall and 6 microns at the
> bottom.
>
> I do not use any mask for now. The copper is plated onto the whole
> wafer.
> I have tried many plating schemes such as pulse plating and reverse
> pulse plating with pulse periods of 12 to 13 ms.
> I have not tried DC plating however, because I thought it would not
> work.
> I have a seed layer that is deposited by sputtering and my estimate is
> that it is 5000 A thick so I believe the seed layer is not very
> resistive.
> I am using organic additives called PCM+ from the company LeaRonal.
>
> The plating bath has a magnetic stirrer.
>
> The solution is mixed as:
> CuSO4: 75 g/L
> H2SO4: 184 g/L
> PCM: .005 L/L
> HCl: .166 ml/L
>
> I chanced upon a solution to an electroplating problem by Eric Sanjuan
> on this website, and I'm hoping someone can help me.
> Also, how often would one need to make new baths.I mean in terms of
> Thanking you,
> Sajid
>